Entamoeba invadens: Enhancement of excystation and metacystic development by cytochalasin D

Effects of three actin-modifying drugs, cytochalasin D, latrunculin A, and jasplakinolide, on the excystation and metacystic development in vitro of E ntamoeba invadens were examined by transfer of the cysts to growth medium w ith the drugs. Cytochalasin D unexpectedly increased the number of metacyst ic amoebae of E. invadens strain IP-1 during incubation. Metacystic develop ment, which was determined by the number of nuclei of metacystic amoebae, w as faster in the culture with cytochalasin D than in the culture without th e drug. These results suggest that cytochalasin D enhances the excystation and metacystic development. In contrast, latrunculin A and jasplakinolide i nhibited these process. No excystation occurred in encystation. medium even in the presence of cytochalasin D, suggesting that growth medium is essent ial for excystation. Excystation was further enhanced when the cysts were i ncubated with cytochalasin D before culture in growth medium with the drug. The enhancing effect of cytochalasin D on the excystation and metacystic d evelopment was abrogated by jasplakinolide. Thus, the results indicate that cytochalasin D, unlike latrunculin A and jasplakinolide, caused enhancemen t of the excystation and metacystic development of this parasite. (C) 2001 Academic Press.